PHYS 106 Exam 2

What does the average energy of photons in an X-ray beam represent?\

The weighted average energy of the photons, representing the energy of a monoenergetic beam with equivalent penetration capability.

How does the maximum photon energy compare with the average energy in a bremsstrahlung spectrum?\

Maximum energy equals the incident electron energy and applied kVp. Average energy is always lower.

What electrical conversion allows electrons to flow in only one direction through an X-ray tube?\

Converting alternating current (AC) into direct current (DC).

Why can using more of an AC cycle increase X-ray production efficiency?\

More of the electrical cycle is utilized to produce X-rays.

How can changing the electrical waveform improve X-ray beam quality?\

It produces a more consistent beam with fewer low-energy photons.

What happens when low-energy photons are selectively removed from an X-ray beam?\

Patient exposure to unnecessary radiation decreases, and the beam becomes harder with higher average energy.

What material is typically used to remove low-energy photons from an X-ray beam?\

Aluminum.

How does increasing the peak tube voltage affect X-ray production efficiency?\

Efficiency increases because higher-energy electrons produce more X-rays and higher-energy X-rays.

How does increasing the atomic number of the target material affect X-ray generation?\

More X-rays are produced per incident electron, and their average energy increases.

What general relationship exists between target atomic mass or atomic number and X-ray generation efficiency?\

As atomic mass or atomic number increases, X-ray generation efficiency generally increases.

What shape does a bremsstrahlung spectrum have, and where does it end?\

It is a continuous spectrum of photon energies with a sharp maximum-energy cutoff equal to the applied kVp.

What characterizes an unfiltered bremsstrahlung spectrum?\

It contains a broad range of photon energies, including many low-energy photons.

How does filtering change the shape and energy distribution of a bremsstrahlung spectrum?\

It removes many low-energy photons, producing a harder spectrum with a higher average energy.

Approximately what fraction of the maximum energy is the average energy in a bremsstrahlung spectrum?\

About one-third of the maximum energy.

What is the movement of electric charge through a conductor called, and what is its unit?\

Electric current; measured in amperes (A), or amps.

What does electrical potential represent, and what is its unit?\

Potential energy per unit charge; measured in volts (V).

What does electrical power measure, what is its unit, and how is it calculated from voltage and current?\

The rate at which energy is used or produced; measured in watts (W). P = V × I.

What happens to total resistance when resistors are connected in series?\

The individual resistances add together, increasing total resistance.

What happens to total resistance when resistors are connected in parallel?\

The reciprocals of the resistances add together, decreasing total resistance.

How does current change when resistance increases or decreases, assuming voltage remains constant?\

Current decreases as resistance increases and increases as resistance decreases.

How does current change in series and parallel circuits according to the review sheet?\

Current decreases in series circuits and increases in parallel circuits.

What equation combines voltage, current, and power, and when should it be used?\

P = VI. Use it when voltage and current are known or needed.

What equation calculates power from current and resistance, and when should it be used?\

P = I²R. Use it when current and resistance are known or needed.

What equation calculates power from voltage and resistance, and when should it be used?\

P = V²/R. Use it when voltage and resistance are known or needed.

Which negatively charged X-ray tube electrode contains a heated filament and a component that directs electrons?\

The cathode.

What happens when the filament inside the X-ray tube is heated?\

It emits electrons.

What is the purpose of the shaped component surrounding the filament?\

The focusing cup directs and focuses electrons toward the anode.

Which positively charged X-ray tube electrode receives electrons and produces X-rays?\

The anode, which typically contains a rotating disc made of a high-atomic-number material such as tungsten.

What factors are influenced by the angle of the X-ray tube target?\

The effective focal spot size and the distribution of X-rays.

What is the effective focal spot size?\

The apparent size of the X-ray source when viewed from the perspective of the film or detector.

How does a smaller target angle affect the effective focal spot and heat distribution?\

It creates a smaller effective focal spot for sharper images but concentrates heat over a smaller area.

How does a steeper target angle affect heat distribution and exposure capability?\

It distributes the electron beam over a larger area, allowing higher X-ray intensities and shorter exposure times, but may slightly reduce image sharpness.

Why is X-ray intensity different across the field from the anode side to the cathode side?\

The angled anode attenuates X-rays traveling through it more on the anode side, so intensity is greater on the cathode side.

How can the effects of uneven X-ray intensity across the field be mitigated?\

Proper collimation and positioning.

What device changes voltage to the level required for X-ray production?\

A transformer, which increases or decreases voltage in an electrical circuit.

What physical process produces a voltage in a conductor when its magnetic field changes?\

Electromagnetic induction.

What is the relationship between a transformer's primary and secondary voltages and coil turns?\

Vs/Vp = Ns/Np.

If a transformer's output voltage increases by a factor of x, how does its secondary coil turn count change relative to its primary coil?\

The turns ratio increases by the same factor x. A voltage decrease by a factor of x corresponds to a decrease in turns ratio by that factor.

What is the SI unit used to measure magnetic field strength?\

Tesla (T).

What electrical component stores and releases energy in the form of charge?\

A capacitor.

How can a circuit component reduce voltage fluctuations or store energy for later use?\

A capacitor can smooth voltage fluctuations through filtering or store electrical energy for later use.

What electrical component permits current to flow in only one direction?\

A diode.

What is the main purpose of using a one-way current component in an X-ray circuit?\

Rectification, converting AC into DC.

What are semiconductor holes, and how are they classified electrically?\

They are absences of electrons in a material and act as positive charge carriers in p-type material.

How do moving electrons and holes contribute to current in a diode?\

Their movement allows current to flow in one direction; the review sheet describes this as from n-type to p-type.

What is the fluctuation in an X-ray generator's output voltage called?\

Voltage ripple.

How does a larger variation in tube voltage affect the X-ray beam and image quality?\

It creates a wider range of X-ray energies and can reduce image quality.

What causes fluctuations in the voltage after AC has been converted to DC in an X-ray generator?\

An insufficient number of electrical phases after rectification.

What does the product of tube current and exposure time determine?\

mAs (milliampere-seconds); it directly affects the number of X-rays produced.

What happens to the number of X-rays produced when mAs increases or decreases?\

Increasing mAs increases X-ray quantity; decreasing mAs reduces X-ray quantity.

Which exposure factor primarily determines X-ray photon energy?\

kVp (kilovolt peak).

What happens to X-ray energy when kVp increases or decreases?\

Increasing kVp raises X-ray energy; decreasing kVp lowers X-ray energy.

How do mAs and kVp differ in their main effects on the X-ray beam?\

mAs primarily controls X-ray quantity; kVp primarily controls X-ray energy and quality.

How does faster rotation of the anode affect exposure time and heat management?\

It distributes the electron beam over more of the anode, improves heat dissipation, and allows shorter exposure times and higher X-ray intensities without overheating.

How does using only half of an AC cycle affect X-ray exposure time?\

Half-wave rectification uses only half the cycle, leaving the tube off for half the time and effectively doubling exposure time compared with full-wave rectification.

How does using both halves of an AC cycle affect X-ray exposure time?\

Full-wave rectification produces X-rays throughout the electrical cycle and reduces exposure time compared with half-wave rectification.

How does a high-frequency generator affect tube voltage, beam consistency, and exposure time?\

It produces nearly constant tube potential with minimal voltage ripple, allowing shorter exposure times and better image quality.

How does anode rotation help prevent localized overheating during an exposure?\

It distributes the electron beam and resulting heat over a larger anode area.

What is the relationship between anode target angle, effective focal spot size, and image sharpness?\

A smaller target angle produces a smaller effective focal spot and sharper images, while concentrating heat over a smaller area.

How does the angle of the anode influence the intensity of X-rays reaching different parts of the image field?\

X-rays traveling through more anode material are more attenuated, resulting in greater intensity on the cathode side than on the anode side